This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To determine how sexual communication occurs between naturally bonded monogamous primates.[unreadable] [unreadable] Smelling isolated scent secretions from female marmosets will stimulate the arousal centers in the brain. The brain [unreadable] response initiates both behavioral and hormonal changes in males. Within 30 minutes of smelling the arousal [unreadable] signals, male marmosets show an increase in testosterone but not cortisol. We found that pairbonded males with [unreadable] offspring responded the least while paired males with no offspring responded more. The biggest responders were [unreadable] the single males. These data suggest that a male's social condition influences how he responds to sexually relevant [unreadable] cues.Male cotton-top tamarins anticipate their mate's ovulatory period. Female tamarins generally ovulate and [unreadable] conceive within two weeks following birth of previous infants. Examining male daily urinary hormones around the [unreadable] time of ovulation indicated that males show increased levels of testosterone, DHT and estradiol before the female [unreadable] ovulated and during the follicular phase of the cycle. Chemical cues appear to be released during the folliculat [unreadable] phase and the male responds with increased androgen. The androgens stimulate spermatogenises and prepares [unreadable] the male to optimize mating. This research relied on WNPRC Assay Services.